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iOptron CEM60-EC

Centre-Balanced Equatorial Mount - concept

In spring 2013 the iOptron Corporation launched the ZEQ25 - the first of their new range of centre-balanced equatorial mounts.  Also called Z-mounts because of the distinctive shape made by the mount head and the counterbalance bar, the mounts are a development of the English Cross Axis design.  The English Cross Axis is very stable but because the counterweight sits below the telescope it is not very portable. iOptron’s development is to move the counterweight to one end of the right ascension axis allowing for a much more compact design.  Also tagged the Chinese Equatorial Mount, the design places the payload closer to the centre of gravity than is the case for the German Equatorial meaning that the centre-balanced mount has good natural stability and a high payload capacity for its weight.

A year later, in early 2014, iOptron added the CEM60 to the Z-mount range.  The number refers to the rated payload for visual use of 60 lbs.

Selecting the mount

I had used a Celestron CGEM DX for several years and while it is a very solid mount it was operating at its limits for longer focal length imaging even after a DIY hypertune.  So I was in the market for a new mount.

I considered a number of options including the Mesu 200, AstroPhysics Mach 1, 10Micron GM1000, and even the ASA60DDM.  I was attracted to the single fork design of the Avalon M-Uno especially as it features a full belt driven design, doesn’t require a meridian flip, and uses the SynScan handset making it compatible with EQMOD.  But the mount won’t carry my 11” EdgeHD scope with the Celrestron 0.7 reducer attached so it was eventually discounted.

I settled on the CEM60 as it is a portable mount capable of carrying an 11” SCT - the mount is rated at 27.2 kg (60lbs) and my heaviest imaging rig is 16.5 kg so I am hoping that I should be within the limits for imaging - and promises high performance with lots of features.  I was impressed that iOptron guarantee peak-to-peak periodic error performance and provide a printout with each mount, that they are instigating vigorous quality control, that the mount head is equipped with a 4 port USB hub and 12 volt power outlets to help cable management, and that they allowed their beta testers to openly post their experiences.  In addition to that I had become pretty annoyed that Celestron and several other big name manufacturers have distribution arrangements that mean European customers are charged considerably higher prices than US consumers even though manufacturing is done in China.  With iOptron, European pricing is on a par with that in the US when shipping, duty, and VAT are taken into account.

At the time I bought it in April 2014 the CEM60 was a brand new line.  The UK distributor decided to delay stocking the mount until later production runs so that any initial production issues could be addressed -which is quite understandable - but I wanted to be an early adopter and to see whether the mount lives up to its billing so I ordered direct from iOptron and I believe mine was one of the first consumer mounts delivered to the UK.  This is obviously a risk, but a calculated one.

Tripod adapter

Like most high-end mounts the CEM60 does not ship with a tripod.  A portable pier is available but I often set up on fairly rough ground so this option didn’t suit me too well.  A field tripod is also available but was out of stock at UK retailers when I ordered my mount and in any case appeared much less substantial than the tripod from my CGEM DX.  I therefore decided to have an adapter made up that would allow me to use the CEM60 with my CGEM DX tripod. JTechDesign is machining up the adapter for me from aluminium plate.

Galaxies Nebulae Planetary Nebulae Solar Planetary Lunar

Arrival and unboxing

My mount arrived direct from the iOptron manufacturing facility in Nanjing,

China via DHL.  There were two boxes: one containing the 9.5 kg counterweight and a second containing the mount itself.

The box containing the counterweight was slightly damaged but the counterweight itself is contained in another inner box and very well protected with packaging material.  The flight case supplied with the mount is much better quality than I was expecting and the finish on the mount is perfectly acceptable so everything looked just as it should inside.

I was looking forward to seeing the periodic error readout.  The specification for this version of the mount is 0.5 arcsecs RMS and the graph supplied with mine reports RMS of 0.338 arcsecs and peak-to-peak performance of +/- 1 arcsec.  If that carries through to real world performance I’ll be absolutely delighted (though if is, of course, a big word…)


I’ve written a full review of the CEM60 which I will periodically update and I am also blogging my experience with the mount.  The UK weather has been pretty poor, though, so progress has been slow...